It is fitting that the obituary of Andrew Roth, who has died aged 91 of prostate cancer, should appear on this page. Not only did he write many of the obituaries of politicians published by the Guardian from 1996 onwards, but he also provided facts and quotations used by dozens of other obituarists and profile writers. The material for this shameless plagiarism was made available in his regularly updated, multi-volume Parliamentary Profiles, a work which has held pride of place on the desks of countless political journalists since 1955.

Yet it is doubtful if many of the hacks who stole chunks of Andy's tightly written, meticulously researched profiles were aware of the colourful career that brought him to London in the first place, and led to his becoming a small but vital part of British parliamentary democracy. Strangely, we owe it to the infamous Senator Joe McCarthy, whose grotesque witch-hunts drove Andy to abandon his native America.

He was born in the Bronx, New York, the son of two Jewish-Hungarian immigrants, Emil and Bertha Roth, who came to the US to escape Jewish orthodoxy rather than anti-semitism. His father was a waiter in a Lower East Side diner, whose patrons resembled Harry the Horse, Bookie Bob and the other clientele of Damon Runyon's ficititious Mindy's restaurant.

Andy became involved with the local Democratic party and thus learned about politics from the basement up. From the College of the City of New York, he went on to Columbia University to study far eastern history and Chinese. This became a valuable asset when war with Japan loomed, and he was soon approached by the US navy with the offer of a commission if he would learn Japanese. By the time of the Japanese attack on Pearl Harbor in December 1941, Andy was on a year-long Japanese course at Harvard, and was then promptly recruited to the navy's code-cracking department in Washington. There he got to know Philip Jaffe, the editor of an obscure magazine called Amerasia, which later came under the scrutiny of the FBI for suspected pro-communist sympathies. Both Jaffe and Andy were arrested, and although Andy was later released, he was dumped by the navy.

So he set out to write Dilemma in Japan (1945), travelling widely and earning his keep as a freelance journalist for the leftish-liberal Nation magazine – and also, occasionally, for what was then the Manchester Guardian. While abroad, he read a report in the New York Times saying that McCarthy was proposing to reopen the Amerasia case as part of his hunt for undercover reds.

Andy phoned a lawyer friend, who advised him to go to London and stay there until the McCarthyite hysteria had blown itself out. He duly did so in 1950, set up house in West Hampstead, and scarcely moved thereafter. In 1966 he took UK citizenship and declined a subsequent offer from the state department to restore his US passport. In 2005 he learned that in 1946 the FBI had arranged for him to be tailed by three women, British, French and Dutch, of whom only the last proved to be a full-blown Mata Hari.

He found that few of the US newspapers for which he had written were still prepared to publish his work. Worse still, the far eastern press were not interested in reports about UK politics. So Andy looked for a niche in British journalism, and found it by offering profiles of MPs to regional newspapers. The idea prospered, and he decided to publish the profiles independently. Thus Parliamentary Profiles was born, to the infinite benefit of everyone.

Well, nearly everyone. Besides the profiles, Andy started a weekly newsletter called Westminster Confidential. Early in its existence, it attracted the fury of the Conservative party establishment by launching the first specific report linking the war minister John Profumo with the dancer and callgirl Christine Keeler. It happened almost by accident, when a big scoop suddenly collapsed on the point of deadline, and a quick substitute was needed.

Andy had been passed a copy of a compromising letter from Profumo to Keeler by the Tory MP Henry Kirby. He decided to use the story, and only discovered later that it had already been unsuccessfully hawked round Fleet Street. Andy was summoned before the Conservative chief whip, Martin Redmayne, and threatened with expulsion from the lobby. He was saved when the story broke on the floor of the Commons.

Work for established publications came as political correspondent for the Manchester Evening News (1972-84) and the New Statesman (1984-97). Andy also produced a shelf-full of books, cheerfully challenging the vested interests and oversize personalities that he observed at Westminster. Among them were The Business Background of MPs (seven editions, 1959-80), Enoch Powell, Tory Tribune (1970), Lord On the Board (1972) and Sir Harold Wilson: Yorkshire Walter Mitty (1977).

Andy's profile service became a pillar of the parliamentary system. His brief sketches of MPs are famed for their pithy and often extremely funny characterisations. Describing a mean Tory MP as a "lovable tightwad" who bought his clothes at jumble sales, he recorded that when the MP asked a colleague to guess how much he had paid for his suit, he was told: "I don't know, but I hope the corpse was at least cold."

But his American origins sometimes hampered him. When he labelled a Labour MP with a pronounced stoop as "bent", the row reverberated for weeks. Roth continued to be one of nature's New Yorkers, hardly changing his Bronx accent in half a century. Bearded and bespectacled, he could look professorial in repose. But when he laughed – which was a lot – he looked like an elderly satyr. He will be missed at Westminster, and not just for his profiles.

His work on Westminster Confidential continued until the house rose last week. His first two marriages, to Renee Knitel and Tilly Friederich, ended in divorce. He is survived by his third wife, Antoinette Putnam, whom he married in 2004; by his daughter, Terry, and his son, Neil, from his second marriage; and by his grandchildren, Lauren, Jesse and Melissa.